Polymer interlayers comprising a compatibilizer

ABSTRACT

A polymer composition comprising a first poly(vinyl butyral) resin having a first residual hydroxyl content; a second poly(vinyl butyral) resin having a second residual hydroxyl content; a plasticizer; and at least one compatibilizer, such as an anhydride compatibilizer; wherein the difference between the first and second residual hydroxyl contents is at least 2 wt. %, and wherein the polymer composition has a percent haze of less than 5%. The use of a compatibilizer reduces or minimizes the optical defects, such as haze and color, without sacrificing other characteristics of the composition. The composition may be used in an interlayer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This disclosure is related to the field of polymer interlayers formultiple layer panels and multiple layer panels having at least onepolymer interlayer sheet. Specifically, this disclosure is related tothe field of polymer interlayers comprising a compatibilizer.

2. Description of Related Art

Multiple layer panels are generally panels comprised of two sheets of asubstrate (such as, but not limited to, glass, polyester, polyacrylate,or polycarbonate) with one or more polymer interlayers sandwiched therebetween. The laminated multiple layer glass panels are commonly utilizedin architectural window applications and in the windows of motorvehicles and airplanes, and in photovoltaic solar panels. The first twoapplications are commonly referred to as laminated safety glass. Themain function of the interlayer in the laminated safety glass is toabsorb energy resulting from impact or force applied to the glass, tokeep the layers of glass bonded even when the force is applied and theglass is broken, and to prevent the glass from breaking up into sharppieces. Additionally, the interlayer may also give the glass a muchhigher sound insulation rating, reduces UV and/or IR light transmission,and enhances the aesthetic appeal of the associated window. In regard tothe photovoltaic applications, the main function of the interlayer is toencapsulate the photovoltaic solar panels which are used to generate andsupply electricity in commercial and residential applications.

In order to achieve the desired and optimal sound insulation for theglass panel, it has become common practice to utilize multilayeredinterlayers with at least one soft “core” layer sandwiched between twomore rigid “skin” layers. Theses layers of the interlayer are generallyproduced by mixing a polymer resin such as poly(vinyl butyral) with oneor more plasticizers and melt processing the mix into a sheet by anyapplicable process or method known to one of skill in the art,including, but not limited to, extrusion, with the layers being combinedby processes such as co-extrusion and lamination. Other additionalingredients may optionally be added for various other purposes. Afterthe interlayer sheet is formed, it is typically collected and rolled fortransportation and storage and for later use in the multiple layer glasspanel, as discussed below.

Contemplated polymer interlayers include, but are not limited to,polyvinyl acetals (PVA) (such as poly(vinyl butyral) (PVB) or poly(vinylisobutyral), an isomer of poly(vinyl butyral) (which may be referred asPViB or PVisoB), polyurethane (PU), poly(ethylene-co-vinyl acetate)(EVA), polyvinylchloride (PVC), polyethylenes, polyolefins, ethyleneacrylate ester copolymers, poly(ethylene-co-butyl acrylate),copolyesters, silicone elastomers, epoxy resins, and any acid copolymerssuch as an ethylene/carboxylic acid copolymer and its ionomers, derivedfrom any of the foregoing possible thermoplastic resins. PVB and itsisomer polyvinyl isobutyral, polyvinyl chloride, ionomers, andpolyurethane are preferred polymers generally for interlayers.

Multilayer laminates can include multiple layer glass panels andmultilayer polymer films. In certain embodiments, the multiple polymerfilms in the multilayer laminates may be laminated together to provide amultilayer film or interlayer. In certain embodiments, these polymerfilms may have coatings, such as metal, silicone or other applicablecoatings known to those of ordinary skill in the art. The individualpolymer films which comprise the multilayer polymer films may belaminated together using an adhesive as known to those of ordinary skillin the art.

The interlayer may be a single layer, a combination of more than onesingle layer, a multilayer that has been coextruded, multiple layerslaminated together to form a multilayer interlayer, a combination of atleast one single layer and at least one multilayer, or a combination ofmultilayer sheets.

The following offers a simplified description of the manner in whichmultiple layer glass panels are generally produced in combination withthe interlayers. First, at least one polymer interlayer sheet (single ormultilayer) is placed between two substrates and any excess interlayeris trimmed from the edges, creating an assembly. It is not uncommon formultiple polymer interlayer sheets or a polymer interlayer sheet withmultiple layers (or a combination of both) to be placed within the twosubstrates creating a multiple layer glass panel with multiple polymerinterlayers. Then, air is removed from the assembly by an applicableprocess or method known to one of skill in the art; e.g., through niprollers, vacuum bag or another deairing mechanism. Additionally, theinterlayer is partially press-bonded to the substrates by any methodknown to one of ordinary skill in the art. In a last step, in order toform a final unitary structure, this preliminary bonding is renderedmore permanent by a high temperature and pressure lamination process, orany other method known to one of ordinary skill in the art such as, butnot limited to, autoclaving.

Often, polymer interlayers that do not meet all of the desiredproperties (for example, off grade material that does not meet at leastone property specification) or polymer interlayer trim, (both referredto hereinafter as “recycle” or “recycled” material) may be recycledduring the production process, such as during the extrusion process. Therecycled material may be fed directly back into the extruder or mixer,or it may be further processed, such as chopped into small pieces orprocessed into pellets or other shapes, and then mixed with the resin(s)and plasticizer (and any other additives) prior to the extruder or othermixing device. Depending on the particular quality problem (such ascontamination, moisture level, color, and the like), different levels ofrecycled material may be used. For example, if the recycled material hasa high level of haze, lower levels may be incorporated into the mixtureso that the recycled material does not increase the haze level in thefinal product, or if the recycled material includes multiple resin typesand/or multiple plasticizers, the recycled material may be incompatiblewith the particular product being produced. For example, PVBformulations containing non-standard plasticizer and/or PVB resin havingdifferent residual hydroxyl levels will not be compatible with thestandard formulations.

Poly(vinyl butyral) (PVB) is a copolymer containing vinyl acetate, vinylalcohol and vinyl butyral components. The vinyl acetate component is theresult of residual groups remaining after the hydrolysis of poly(vinylacetate) to form poly(vinyl alcohol). The poly(vinyl alcohol) is thenused in the process. The vinyl alcohol component is the result ofresidual groups remaining after acetalizing the poly(vinyl alcohol) withbutyraldehyde to form poly(vinyl butyral). The content of residual vinylacetate components in commercial grade PVB is generally in the range ofabout 1 to 15 wt. %, more commonly less than 4 wt. %. In the past,standard commercial grade PVB for multiple layer glass panels generallyhad a residual vinyl alcohol (also referred to as residual hydroxyl)content (% PVOH) of about 18 to 21 wt. %, more commonly about 18 to 19.5wt. %. More recently, development of multilayer polymer interlayers forlaminated glass has introduced different and more complicated productconfigurations, especially in polymer interlayers used to help improveacoustic properties (noise reduction) of the polymer interlayer and thefinal multiple layer glass panel. Multiple layer polymer interlayers areoften produced from multiple different resins each having a differentresidual vinyl alcohol and/or residual vinyl acetate level. Thesemultiple layer polymer interlayers have been developed to provideimproved acoustical performance while retaining many of the otherstandard safety glass performance functions. In such multiple layerpolymer interlayers used to improve acoustic performance (among otherimprovements), the resin used in the core (or inner) layer often hasvery low residual vinyl alcohol content, such as % PVOH of about 10 to11 wt. %, while the resin used in the skin (outer) layer(s) may have aresidual vinyl alcohol content (% PVOH) of about 18 to 19.5 wt. %. Othervariations, different numbers of resins, or resins having differentlevels of residual vinyl alcohol content may also be used. Additionally,the multilayer interlayer may have different configurations of resins inthe individual layers as desired, such as, for example a core layerresin having a higher % PVOH (such as 19.5 to 30 wt. %) than the skinlayer (having lower residual vinyl alcohol content, such as % PVOH ofabout 10 to 19.5 wt. %).

One of the problems in the manufacture of polymer interlayers usingcertain types, or mixtures of certain types, of resins or recycledinterlayer sheet comprising different resin and/or plasticizer types ishaze or poor optical clarity. Haze is caused by a number of differentfactors, but one cause is the difference in levels of residual hydroxylcontent in the resins used to produce the polymer interlayers. Differenttypes of resins are used to produce polymer interlayers with differentperformance properties, such as adhesion, impact resistance, acousticproperties, mechanical properties, as well as other properties. Thedifferent resin types may have different levels of residual hydroxylcontent, residual vinyl acetate content, or even different aldehydes ifthey were acetalized with different aldehyde groups. These differentresins may also have different refractive indices.

The refractive index of a substance, such as an interlayer, is themeasure of the speed of light through the substance with respect to thespeed of light in vacuum. If there is a difference between therefractive index of the layers of a multiple layer interlayer, forexample, because different resins are being used in the individuallayers, then when the multilayer interlayer is recycled (melt mixingback into the polymer interlayer), the resulting polymer interlayer willoften have high haze due to incompatibility between different resins.

Clarity of the interlayer, and more importantly, the glazing or multiplelayer panel, is one of the critical quality parameters. Clarity isdetermined by measuring the level of haze in the multiple layer panel,as further described below. The level of haze must be very low so thatthe multiple layer panel is clear (and often transparent). In additionto haze, there are other optical quality defects, such as visibleoptical defects in the interlayer, that cause light scattering and makethe defect visible to the eye that may cause optical distortion in theglass panel as well. Both haze and other visible optical defects arecaused by light scattering due to the blending or mixing differentpolymers or plasticizer together, or the contamination from suchdifferent polymers and/or plasticizer where there is a sufficientlylarge difference in the refractive index between the different polymersor plasticizers, or the matrix and the contaminants.

The presence of haze or other optical quality defects in the finalunitary structure of a multilayer laminate glass panel can beproblematic because a certain degree of optical quality is necessary inmany (if not most) of the end-use commercial applications of multilayerlaminate glass panels (e.g., vehicular, aeronautical and architecturalapplications). Thus, the creation of multilayer laminate glass panelswith commercially acceptable levels of low haze and good clarity isparamount in the art of multiple layer glass panel manufacturing.Because of the different properties and types of resins used to producemultiple layer polymer interlayers, such as a trilayer polymerinterlayer having a soft core layer and harder skin layers, the multiplelayer polymer interlayers, are difficult to reuse or recycle in largequantities. Only small amounts or percentages of the multiple layerpolymer interlayers have been successfully used in the past.Additionally, it is often hard to reuse or recycle large quantities ofunknown or varying recycle materials for the same reasons because thematerials may be incompatible.

Other methods for recycling multilayer materials having different resintypes have also been tried. For example, attempts to separate the resinand plasticizer by extraction of the plasticizer and recovery of theresin has been tried, but the process is not cost effective and is veryresource intensive. The recycle materials could be used for otherapplications where haze and/or clarity are not a concern, but most timesthis approach is not economical because the PVB interlayer would then besold at a lower value and would lose too much of its original value.

Summarized, optical quality defects such as haze and other visibleoptical defects are common problems in the field of multiple layer glasspanels, particularly those used in applications which require higherlevels of optical or visual quality. It is now common to use amultilayer interlayer in order to provide high performance laminateshaving specialized properties, such as improved acoustics. The use ofmultilayer interlayers, however, very often results in difficulties whenattempting to recycle the multilayer materials because only a smallamount of the recycle material could be recycled due to opticalproblems, such as haze and/or other optical quality defects. As aresult, large quantities of recycle materials have to be disposed of inother ways, such as sale at reduced value or by landfilling, with littleor no value (and potentially an added cost). Accordingly, there is aneed in the art for improving the recyclability of multiple layerpolymer interlayer without a reduction in optical, mechanical, andacoustic characteristics of a polymer interlayer, and a need for thedevelopment of process to recycle multiple layer polymer interlayer.

SUMMARY OF THE INVENTION

Because of these and other problems in the art, described herein, amongother things is a polymer composition comprising: a first and a secondpoly(vinyl butyral) resin, wherein the poly(vinyl butyral) resins havedifferent residual hydroxyl contents; at least one plasticizer and atleast one compatibilizer. The polymer composition has a percent haze ofless than 5%.

In an embodiment, a polymer composition comprises: a first poly(vinylbutyral) resin having a first residual hydroxyl content; a secondpoly(vinyl butyral) resin having a second residual hydroxyl content; aplasticizer; and at least one compatibilizer; wherein the differencebetween the first and second residual hydroxyl contents is at least 2wt. %, and wherein the polymer composition has a percent haze of lessthan 5% (as measured in accordance with ASTM D1003-Procedure B usingIlluminant C). In embodiments, the polymer composition comprises fromabout 0.01 wt. % to about 10 wt. % compatibilizer, or from about 0.05 toabout 5 wt. % compatibilizer. In embodiments, the difference between thefirst and second residual hydroxyl contents is at least 3 wt. %, or atleast 4 wt. %, or at least 5 wt. %, or at least 6 wt. %, or at least 7wt. %, or at least 8 wt. % or more. In embodiments, the polymercomposition has a percent haze of less than about 4.5%, or less thanabout 4%, or less than about 3.5%, or less than about 3%, or less thanabout 2.5%, or less than about 2%, or less than about 1.5%, or less thanabout 1%, or less than about 0.5%.

In embodiments, the compatibilizer is an anhydride compatibilizer. Inembodiments, the compatibilizer comprises at least two anhydrides.

In embodiments, the compatibilizer comprises at least one anhydridehaving Structure (3), Structure (4), Structure (5) or Structure (6):

wherein R may be hydrogen or a saturated or unsaturated carbon chain offrom 1 to 16 carbon atoms.

In an embodiment, the compatibilizer is at least one ofhexahydro-4-methylphthalic anhydride, hexahydrophthalic anhydride,phthalic anhydride, 3,4,5,6-tetrahydrophthalic anhydride, or2-octen-1-ylsuccinic anhydride. In an embodiment, the compatibilizercomprises a mixture of hexahydrophthalic anhydride andhexahydro-4-methylphthalic anhydride.

In an embodiment, a multiple layer polymer interlayer comprising: afirst layer comprising a first poly(vinyl butyral) resin having a firstresidual hydroxyl content and a plasticizer; a second layer comprising asecond poly(vinyl butyral) resin having a second residual hydroxylcontent and a third poly(vinyl butyral) resin having a third residualhydroxyl content, a plasticizer, and at least one compatibilizer;wherein the difference between the second and third residual hydroxylcontents is at least 2 wt. %, and wherein the polymer interlayer has apercent haze of less than 5% (as measured in accordance with ASTMD1003-Procedure B using Illuminant C). In embodiments, the polymercomposition comprises from about 0.01 wt. % to about 10 wt. %compatibilizer, or from about 0.05 to about 5 wt. % compatibilizer. Inembodiments, the difference between the first and second residualhydroxyl contents is at least 3 wt. %, or at least 4 wt. %, or at least5 wt. %, or at least 6 wt. %, or at least 7 wt. %, or at least 8 wt. %or more. In embodiments, the polymer composition has a percent haze ofless than about 4.5%, or less than about 4%, or less than about 3.5%, orless than about 3%, or less than about 2.5%, or less than about 2%, orless than about 1.5%, or less than about 1%, or less than about 0.5%.

In embodiments, the compatibilizer is an anhydride compatibilizer. Inembodiments, the compatibilizer comprises at least two anhydrides.

In embodiments, the compatibilizer comprises at least one anhydridehaving Structure (3), Structure (4), Structure (5) or Structure (6):

wherein R may be hydrogen or a saturated or unsaturated carbon chain offrom 1 to 16 carbon atoms.

In an embodiment, the compatibilizer is at least one ofhexahydro-4-methylphthalic anhydride, hexahydrophthalic anhydride,phthalic anhydride, 3,4,5,6-tetrahydrophthalic anhydride, or2-octen-1-ylsuccinic anhydride. In an embodiment, the compatibilizercomprises a mixture of hexahydrophthalic anhydride andhexahydro-4-methylphthalic anhydride.

In an embodiment, a polymer composition comprises: a first poly(vinylbutyral) resin having a first residual hydroxyl content; a secondpoly(vinyl butyral) resin having a second residual hydroxyl content; aplasticizer; and from 0.01 to 10 wt. % of at least one anhydridecompatibilizer; wherein the difference between the first and secondresidual hydroxyl contents is at least 2 wt. %, and wherein the polymercomposition has a percent haze of less than 5% (as measured inaccordance with ASTM D1003-Procedure B using Illuminant C). Inembodiments, the difference between the first and second residualhydroxyl contents is at least 3 wt. %, or at least 4 wt. %, or at least5 wt. %, or at least 6 wt. %, or at least 7 wt. %, or at least 8 wt. %or more. In embodiments, the polymer composition has a percent haze ofless than about 4.5%, or less than about 4%, or less than about 3.5%, orless than about 3%, or less than about 2.5%, or less than about 2%, orless than about 1.5%, or less than about 1%, or less than about 0.5%. Inembodiments, the polymer composition comprises from about 0.05 to about5 wt. % compatibilizer.

In embodiments, the compatibilizer is an anhydride compatibilizer. Inembodiments, the compatibilizer comprises at least two anhydrides.

In embodiments, the compatibilizer comprises at least one anhydridehaving Structure (3), Structure (4), Structure (5) or Structure (6):

wherein R may be hydrogen or a saturated or unsaturated carbon chain offrom 1 to 16 carbon atoms.

In an embodiment, the compatibilizer is at least one ofhexahydro-4-methylphthalic anhydride, hexahydrophthalic anhydride,phthalic anhydride, 3,4,5,6-tetrahydrophthalic anhydride, or2-octen-1-ylsuccinic anhydride. In an embodiment, the compatibilizercomprises a mixture of hexahydrophthalic anhydride andhexahydro-4-methylphthalic anhydride.

In an embodiment, a polymer interlayer comprises the polymercomposition. In an embodiment, a multiple layer glass panel comprisesthe polymer interlayer comprising the polymer composition.

In certain embodiments, the rigid substrate is glass. In otherembodiments, the panel may further comprise a photovoltaic cell, withthe interlayer encapsulating the photovoltaic cell.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Described herein, among other things, are compositions comprised ofmixed thermoplastic resins (poly(vinyl butyral)) having differentresidual vinyl alcohol contents, a conventional plasticizer, and atleast one compatibilizer, wherein the composition has excellent clarity.The composition may be used, for example, in a polymer interlayer. Theuse of compatibilizer herein significantly increases the compatibilitybetween different poly(vinyl butyral) resins having different residualvinyl alcohol contents, and creates composition containing multiple PVBresins having low haze without sacrificing other characteristics. Inthis regard, the compatibilizer(s), when selected as a certain type andto have certain properties results in a composition, and in someembodiments an interlayer, having excellent optical clarity as measuredby at least haze. As a result, higher quality, optically clear multiplelayer glass panels are produced, more material is recycled, andoperational efficiency is improved due to the ability to recyclematerial.

Multilayer interlayers, such as a trilayer interlayer, often comprise asoft core (inner) layer specifically designed for acoustic attenuationwith stiffer skin or outer layers. In the interlayer, the plasticizer(such as triethylene glycol di-(2-ethylhexanoate) (3GEH)) in the coreand skin layers often partitions (as it reaches equilibrium state) infavor of the softer layer over the stiffer or harder layer, in aproportion predominated by the characteristics of resins used in skinand core layers. Additionally, to produce the softer core and stifferskin layers, resins having different residual hydroxyl content, andoften widely different hydroxyl content, are used in the layers. Whenthe multilayer interlayer is then recycled and added back into themixture for re-extrusion, the combination of different resins havingpotentially greatly different residual hydroxyl content or thecombination of multiple different resins having different plasticizertypes and amounts and/or different residual hydroxyl contents causeshaze due to the incompatibility of the resins.

To illustrate the difference, a simplified example of this can be shown.In PVB resin, there are vinyl alcohol segments and vinyl butyralsegments. As an example, if the resin used to produce the skin layer hasa residual hydroxyl content of from about 18 to 19 wt. %, and the corelayer has a much lower residual hydroxyl level, such as about 10% to 11wt. %, to produce the softer core, then the number of vinyl alcoholsegments is considerably different in the core and skin layers (8 to 9wt. % different).

In their simplest form, the resins used for the skin and core layers areshown in as Structures (1) and (2).

Structure (1), which has more vinyl alcohol segments (or higher residualvinyl alcohol content), represents the resin used in the skin in theexample previously given, while Structure (2), having fewer vinylalcohol segments (or lower residual vinyl alcohol content), representsthe resin used for the core layer in the example. Structures (1) and (2)are only representative examples for illustration and discussionpurposes and not to scale or necessarily accurate regarding the numberof vinyl alcohol segments or the amount of residual hydroxyl content.

It has been discovered by the inventor that a small amount of acompatibilizer, when added to the mixture of resins and plasticizer(s)prior to extrusion, dramatically increases the compatibility between thedifferent resins, such as the resins used in core and skin layers ofmultilayer polymer interlayers, and helps to reduce haze and otheroptical quality defects (such as reduced light transmission) in thefinal polymer composition or polymer interlayer.

Some terminology used throughout this application will be explained toprovide a better understanding of the invention. The terms “polymerinterlayer sheet,” “interlayer,” and “polymer melt sheet” as usedherein, generally may designate a single-layer sheet or a multilayeredinterlayer. A “single-layer sheet,” as the names implies, is a single(or monolithic) polymer layer extruded as one layer. A multilayeredinterlayer, on the other hand, may comprise multiple layers, includingseparately extruded layers, co-extruded layers, or any combination ofseparately and co-extruded layers. Thus the multilayered interlayercould comprise, for example: two or more single-layer sheets combinedtogether (“plural-layer sheet”); two or more layers co-extruded together(“co-extruded sheet”); two or more co-extruded sheets combined together;a combination of at least one single-layer sheet and at least oneco-extruded sheet; and a combination of at least one plural-layer sheetand at least one co-extruded sheet.

In various embodiments, the polymer composition may be used in aninterlayer that is a single or monolithic interlayer comprising two ormore resins (as discussed above). In embodiments, the single layerinterlayer may comprise two or more PVB resins having different levelsof residual hydroxyl content (such as where the difference between theresidual hydroxyl contents is at least 2 wt. %), or the interlayer maybe a single layer having one or more resins that is then part of amultiple layer interlayer, such as a skin or core layer.

In various embodiments, the polymer composition may be used inmultilayered interlayers where the multilayered interlayer comprises atleast two polymer layers (e.g., a single layer or multiple layersco-extruded) disposed in direct contact with each other, wherein eachlayer comprises a polymer resin, as detailed more fully below. Inembodiments, at least one layer of the multilayer interlayer, such as askin layer or the core layer, comprises two (or more) different resins,such as two PVB resins having different residual hydroxyl contentlevels. As used herein for multilayer interlayers having at least threelayers, “skin layer” generally refers to outer layers of the interlayerand “core layer” generally refers to the inner layer(s). Thus, oneexemplary embodiment would be: skin layer II core layer II skin layer.It should be noted, however, further embodiments include interlayershaving two layers, or more than three layers (e.g., 4, 5, 6, or up to 10individual layers). Additionally, any multilayer interlayer utilized canbe varied by manipulating the composition, thickness, or positioning ofthe layers and the like. For example, in one trilayer polymer interlayersheet, the two outer or skin layers may comprise poly(vinyl butyral)(“PVB”) resin with a plasticizer or mixture of plasticizers, while theinner or core layer may comprise different PVB resin or a differentthermoplastic material with a plasticizer and/or mixture ofplasticizers. Thus, it is contemplated that the skin layers and the corelayer(s) of the multilayered interlayer sheets may be comprised of thesame thermoplastic material or different thermoplastic materials and thesame or different plasticizer or plasticizers. Either or both layers mayinclude additional additives as known in the art, as desired.

Although the embodiments described below refer to the polymer resin asbeing PVB (which includes its isomer, polyvinyl isobutyral), it would beunderstood by one of ordinary skill in the art that the polymer may beany polymer suitable for use in a multiple layer panel. Typical polymersinclude, but are not limited to, PVB, polyurethane, polyvinyl chloride,poly(ethylene-co-vinyl acetate), combinations of the foregoing, and thelike. PVB, polyvinyl chloride, and polyurethane are particularly usefulpolymers generally for interlayers; PVB is particularly suitable whenused in conjunction with the interlayers of this disclosure comprising acompatibilizer, such as an anhydride compatibilizer.

Prior to discussing the addition of the compatibilizer selected toproduce the composition or the interlayer having improved opticalquality, some common components found in a polymer composition and aninterlayer, both generally and in compositions and interlayers of thepresent disclosure, and the formation thereof.

The PVB resin is produced by known acetalization processes by reactingpolyvinyl alcohol (“PVOH”) with butyraldehyde in the presence of an acidcatalyst, separation, stabilization, and drying of the resin. Suchacetalization processes are disclosed, for example, in U.S. Pat. Nos.2,282,057 and 2,282,026 and Vinyl Acetal Polymers, in Encyclopedia ofPolymer Science & Technology, 3rd edition, Volume 8, pages 381-399, byB. E. Wade (2003), the entire disclosures of which are incorporatedherein by reference. The resin is commercially available in variousforms, for example, as Butvar® Resin from Solutia Inc. (which is awholly owned subsidiary of Eastman Chemical Company).

As used herein, residual hydroxyl content (calculated as % PVOH byweight) in PVB refers to the amount of hydroxyl groups remaining on thepolymer chains after processing is complete. For example, PVB can bemanufactured by hydrolyzing poly(vinyl acetate) to PVOH, and thenreacting the PVOH with butyraldehyde. In the process of hydrolyzing thepoly(vinyl acetate), typically not all of the acetate side groups areconverted to hydroxyl groups. Further, reaction with butyraldehydetypically will not result in all hydroxyl groups being converted toacetal groups. Consequently, in any finished PVB resin, there typicallywill be residual acetate groups (as vinyl acetate groups) and residualhydroxyl groups (as vinyl alcohol groups) as side groups on the polymerchain. As used herein, residual hydroxyl content is measured on a weightpercent basis per ASTM 1396.

In various embodiments, the PVB resin comprises about 8 to about 35weight percent (wt. %) hydroxyl groups calculated as % PVOH, or about 9to about 30 wt. %, about 10 to about 22 wt % hydroxyl groups calculatedas % PVOH, although any level or combination of levels of residualhydroxyl groups is possible. The resin can also comprise less than 15wt. % residual ester groups, less than 13 wt. %, less than 11 wt. %,less than 9 wt. %, less than 7 wt. %, less than 5 wt. %, or less than 1wt. % residual ester groups calculated as polyvinyl ester, e.g.,acetate, with the balance being an acetal, such as butyraldehyde acetal,but optionally being other acetal groups, such as an isobutyraldehydeacetal group, or a 2-ethyl hexanal acetal group, or a mix of any two ofbutyraldehyde acetal, isobutyraldehyde, and 2-ethyl hexanal acetalgroups (see, for example, U.S. Pat. No. 5,137,954, the entire disclosureof which is incorporated herein by reference).

For a given type of plasticizer, the compatibility of the plasticizer inthe PVB polymer is largely determined by the hydroxyl content of thepolymer. PVB with greater residual hydroxyl content is typicallycorrelated with reduced plasticizer compatibility or capacity, i.e.,less plasticizer could be incorporated. Conversely, PVB with a lowerresidual hydroxyl content typically will result in increased plasticizercompatibility or capacity, i.e., more plasticizer could be incorporated.For some plasticizer types, such correlation might be reversed.Generally, this correlation between the residual hydroxyl content of apolymer and plasticizer compatibility/capacity will allow for additionof the proper amount of plasticizer to the polymer resin and moreimportantly, the ability to stably maintain differences in plasticizercontent between multiple interlayers. The PVB resin (or resins) of thepresent disclosure typically has a molecular weight of greater than50,000 Daltons, or less than 500,000 Daltons, or about 70,000 to about500,000 Daltons, or about 100,000 to about 425,000 Daltons, as measuredby size exclusion chromatography using low angle laser light scattering.As used herein, the term “molecular weight” means the weight averagemolecular weight.

Various adhesion control agents (“ACAs”) can be used in the interlayersof the present disclosure to control the adhesion of the sheet to glass.In various embodiments of interlayers of the present disclosure, theinterlayer can comprise about 0.003 to about 0.45 parts ACAs per 100parts resin; about 0.01 to about 0.40 parts ACAs per 100 parts resin;and about 0.01 to about 0.10 parts ACAs per 100 parts resin. Such ACAs,include, but are not limited to, the ACAs disclosed in U.S. Pat. No.5,728,472 (the entire disclosure of which is incorporated herein byreference), residual sodium acetate, potassium acetate, magnesiumbis(2-ethyl butyrate), and/or magnesium bis(2-ethylhexanoate).

Other additives (in addition to the compatibilizer disclosed herein) maybe incorporated into the interlayer to enhance its performance in afinal product and impart certain additional properties to theinterlayer. Such additives include, but are not limited to, dyes,pigments, stabilizers (e.g., ultraviolet stabilizers), antioxidants,anti-blocking agents, flame retardants, IR absorbers or blockers (e.g.,indium tin oxide, antimony tin oxide, lanthanum hexaboride (LaB₆) andcesium tungsten oxide), processing aides, flow enhancing additives,lubricants, impact modifiers, nucleating agents, thermal stabilizers, UVabsorbers, dispersants, surfactants, chelating agents, coupling agents,adhesives, primers, reinforcement additives, and fillers, among otheradditives known to those of ordinary skill in the art.

The interlayer can comprise 0 to about 100, 0 to about 80, about 0 to45, about 10 to about 75, about 15 to about 60, about 25 to about 50,about 15 to about 50, about 10 to about 40, about 15 to about 40, about25 to about 38, about 29 to about 32, and about 30 phr (parts perhundred parts resin) plasticizer or a mix of plasticizers. Of course,other quantities can be used as is appropriate for the particularapplication and the desired properties. In various embodiments ofinterlayers of the present disclosure, the interlayer will comprisegreater than 5 phr, about 5 to about 100 phr, about 10 to about 80 phr,about 30 to about 60 phr, or less than 100 phr, or less than 80 phrtotal plasticizer. While the total plasticizer content is indicatedabove, the plasticizer content in the individual layers, such as theskin layer(s) or core layer(s) can be different from the totalplasticizer content. In addition, the individual layers, such as theskin layer(s) and core layer(s), can have different plasticizer typesand plasticizer contents, in the ranges previously discussed, as eachrespective layer's plasticizer content at the equilibrium state isdetermined by the layer's respective residual hydroxyl contents, asdisclosed in U.S. Pat. No. 7,510,771 (the entire disclosure of which isincorporated herein by reference).

In some embodiments, examples of the plasticizer include esters of apolybasic acid or a polyhydric alcohol and phosphates, among others.Suitable plasticizers include, for example, triethylene glycoldi-(2-ethylhexanoate) (“3GEH”), triethylene glycol di-(2-ethylbutyrate),triethylene glycol diheptanoate, tetraethylene glycol diheptanoate,dihexyl adipate, dioctyl adipate, hexyl cyclohexyladipate, diisononyladipate, heptylnonyl adipate, dibutyl sebacate, di(butoxyethyl) adipate,bis(2-(2-butoxyethoxy)ethyl) adipate, and mixtures thereof. In someembodiments, the plasticizer is 3GEH.

In some embodiments, the plasticizer may be a high refractive indexplasticizer. Examples of high refractive index plasticizers include, butare not limited to, esters of a polybasic acid or a polyhydric alcohol,polyadipates, epoxides, phthalates, terephthalates, benzoates,toluoates, mellates and other specialty plasticizers, among others.Examples of suitable plasticizers include, but are not limited to,dipropylene glycol dibenzoate, tripropylene glycol dibenzoate,polypropylene glycol dibenzoate, isodecyl benzoate, 2-ethylhexylbenzoate, diethylene glycol benzoate, propylene glycol dibenzoate,2,2,4-trimethyl-1,3-pentanediol dibenzoate,2,2,4-trimethyl-1,3-pentanediol benzoate isobutyrate, 1,3-butanedioldibenzoate, diethylene glycol di-o-toluoate, triethylene glycoldi-o-toluoate, dipropylene glycol di-o-toluoate, 1,2-octyl dibenzoate,tri-2-ethylhexyl trimellitate, di-2-ethylhexyl terephthalate, bis-phenolA bis(2-ethylhexaonate), and mixtures thereof. Examples of particularlysuitable high refractive index plasticizers are dipropylene glycoldibenzoates, tripropylene glycol dibenzoates, and2,2,4-trimethyl-1,3-pentanediol dibenzoate.

Plasticizers work by embedding themselves between chains of polymers,spacing them apart (increasing the “free volume”) and thus significantlylowering the glass transition temperature (T_(g)) of the polymer resin(typically by 0.5 to 4° C./phr), making the material softer. In thisregard, the amount of plasticizer in the interlayer can be adjusted toaffect the glass transition temperature (T_(g)). The glass transitiontemperature (T_(g)) is the temperature that marks the transition fromthe glassy state of the polymer to the rubbery state. In general, higheramounts of plasticizer loading will result in lower T_(g). Conventionalinterlayers generally have a T_(g) in the range of about 0° C. foracoustic (noise reducing) interlayer to about 45° C. for hurricane andaircraft interlayer applications. A particularly suitable T_(g) forcertain embodiments is in the range of about 28° C. to about 35° C. forthe standard or most common monolithic interlayer applications, andabout −5° C. to about 5° C. for the core layer(s) in the trilayeracoustic interlayer applications.

An interlayer's glass transition temperature is also correlated with thestiffness of the interlayer, and in general, the higher the glasstransition temperature, the stiffer the interlayer. Generally, aninterlayer with a glass transition temperature of 30° C. or higherincreases windshield strength and torsional rigidity. A soft interlayer(generally characterized by an interlayer with a glass transitiontemperature of lower than 30° C.), on the other hand, contributes to thesound dampening effect (i.e., the acoustic characteristics). In someembodiments, the multilayered interlayers can be produced by combiningthese two advantageous properties (i.e., strength and acoustic) byutilizing harder or stiffer skin layers laminated with a softer corelayer (e.g., stiff//soft//stiff) and softer skin layers laminated with astiffer core layer (e.g., soft//stiff//soft). The skin layer in themultilayered interlayer can have glass transition temperatures of about25° C. to about 40° C., about 20° C. to about 35° C., about 25° C. to35° C., about 25° C. or greater, about 30° C. or greater, and about 35°C. or greater, and core layer(s) of about 39° C. or greater, about 35°C. or greater, about 35° C. or less, about 10° C. or less, and about 4°C. or less. For example, the following are some exemplary multilayeredconfigurations:

(T _(g)>25° C.)//(T _(g)<10° C.)//(T _(g)>25° C.);

(25° C.<T _(g)<40° C.)//(T _(g)<10° C.)//(25° C.<T _(g)<40° C.);

(T _(g)<35° C.)//(T _(g)>35° C.)//(T _(g)<35° C.); and

(20° C.<T _(g)<35° C.)//(T _(g)>35° C.)//(20° C.<T _(g)<35° C.).

These configurations are merely exemplary and are in no way meant to belimiting to the types of multilayered configurations. The interlayer ofthe present invention may be a single or monolithic interlayer sheet, oran interlayer sheet having any other number of layers, as desired.

Additionally, it is contemplated that polymer interlayer sheets asdescribed herein may be produced by any suitable process known to one ofordinary skill in the art of producing polymer interlayer sheets thatare capable of being used in a multiple layer panel (such as a glasslaminate or a photovoltaic module or solar panel). For example, it iscontemplated that the polymer interlayer sheets may be formed throughsolution casting, compression molding, injection molding, meltextrusion, melt blowing or any other procedures for the production andmanufacturing of a polymer interlayer sheet known to those of ordinaryskill in the art. Further, in embodiments where multiple polymerinterlayers are utilized, it is contemplated that these multiple polymerinterlayers may be formed through co-extrusion, blown film, dip coating,solution coating, blade, paddle, air-knife, printing, powder coating,spray coating or other processes known to those of ordinary skill in theart. While all methods for the production of polymer interlayer sheetsknown to one of ordinary skill in the art are contemplated as possiblemethods for producing the polymer interlayer sheets described herein,this application will focus on polymer interlayer sheets producedthrough the extrusion and co-extrusion processes. The final multiplelayer glass panel laminate are formed using processes known in the art.

Generally, in its most basic sense, extrusion is a process used tocreate objects of a fixed cross-sectional profile. This is accomplishedby pushing or drawing a material through a die of the desiredcross-section for the end product.

Generally, in the extrusion process, thermoplastic resin andplasticizers, including any of those resins and plasticizers describedabove, as well as any recycled material and the compatibilizer, arepre-mixed and fed into an extruder device. Additives such as ACAs,colorants and UV inhibitors (in liquid, powder, or pellet form) areoften used and can be mixed into the thermoplastic resin or plasticizerprior to arriving in the extruder device. These additives areincorporated into the thermoplastic polymer resin, and by extension theresultant polymer interlayer sheet, to enhance certain properties of thepolymer interlayer sheet and its performance in the final multiple layerglass panel product (or photovoltaic module).

The compatibilizer may be any suitable compatibilizer known in the artthat increases the compatibility of the PVB resins and allows thedifferent resin and/or plasticizer types to be mixed together to producea product having lower haze while also maintaining other desirablephysical and mechanical properties. In other words, any compatibilizermay be used, as long as it functions as a compatibilizer between the twoor more types of resins having different residual vinyl alcohol contentsand/or two or more types of plasticizers. The compatibilizer should beable to modify the resin via reactions or physical interactions so thatthe compatibility between resins (or interlayer sheets containing theresins) having different residual vinyl alcohol contents and/ordifferent plasticizers can be improved.

Examples of compatibilizers include, but are not limited to, anhydrides(such as hexahydrophthalic anhydride, hexahydro-4-methylphthalicanhydride, phthalic anhydride, maleic anhydride, succinic anhydride,glutaric anhydride, citraconic anhydride, 3,4,5,6-tetrahydrophthalicanhydride, and cyclohexanedicarboxylic anhydride), salicyclic acid,boric acid, glycidyl neodecanoate, non-reactive compatibilizers (such asethoxylated nonylphenol), epoxies, di-isocyanates, and combinations ofthe foregoing compatibilizers. The compatibilizer may be liquid orsolid, and may be mixed into the plasticizer prior to mixing with theresin and any recycle material, or added in any other manner desired.

In some embodiments, the compatibilizer may be an anhydridecompatibilizer or a mixture of two or more anhydride compatibilizers.Examples of anhydride compatibilizers include, but are not limited to,those having

In Structures (3), (4), (5) and (6), R may be any desired substituentand can be mono-, di- tri-, tetra-substituted or the like. For example,R may be hydrogen, a saturated or unsaturated carbon chain of from 1 to16 carbon atoms, or from 1 to 10 carbon atoms (such as CH₃, CH₂CH₃), orany other substitution group as desired.

In some embodiments, the compatibilizer may be the mixture of two ormore anhydrides, such as a mixture of anhydrides of Structure (3) andStructure (4), or a mixture of anhydrides of Structure (3) and Structure(5), or a mixture of anhydrides of Structure (3) and Structure (6), or amixture of anhydrides of Structure (4) and Structure (5), or a mixtureof anhydrides of Structure (4) and Structure (6), or a mixture ofanhydrides of Structure (3), Structure (4) and Structure (5), or amixture of anhydrides of Structure (4), Structure (5) and Structure (6),or a mixture of anhydrides of Structure (3), Structure (4), Structure(5) and Structure (6), or a mixture of two or more anhydrides ofStructure (3), or a mixture of two or more anhydrides of Structure (4),or a mixture of two or more anhydrides of Structure (5), or a mixture oftwo or more anhydrides of Structure (6), or any other combination ofanhydrides, depending on the desired properties.

In an embodiment, the anhydride compatibilizer (or at least onecompatibilizer) may be hexahydro-4-methylphthalic anhydride having theStructure (7):

or a phthalic anhydride having the Structure (8):

or 3,4,5,6-tetrahydrophthalic anhydride having the Structure (9):

or 2-octen-1-ylsuccinic anhydride having the Structure (10):

In an embodiment, the anhydride compatibilizer may be ahexahydrophthalic anhydride.

In an embodiment, the anhydride compatibilizer may be a mixture of twoor more anhydrides, such as a mixture of two or more ofhexahydro-4-methylphthalic anhydride, hexahydrophthalic anhydride,phthalic anhydride, 3,4,5,6-tetrahydrophthalic anhydride, and2-octen-1-ylsuccinic anhydride. For example, the compatibilizer may be amixture of hexahydro-4-methylphthalic anhydride and hexahydrophthalicanhydride, or a mixture of phthalic anhydride and3,4,5,6-tetrahydrophthalic anhydride, or a mixture of2-octen-1-ylsuccinic anhydride and hexahydrophthalic anhydride, or amixture of hexahydro-4-methylphthalic anhydride and phthalic anhydride,or a mixture of hexahydro-4-methylphthalic anhydride and3,4,5,6-tetrahydrophthalic anhydride, or any combination of two or moreof anhydrides as desired. In an embodiment, the compatibilizer comprisesa mixture of hexahydrophthalic anhydride and hexahydro-4-methylphthalicanhydride.

The compatibilizer, which in some embodiments may be an anhydridecompatibilizer, is generally added in amounts of from about 0.01 toabout 10 wt. %, or from about 0.05 to about 5 wt. %, or at least about0.01 wt. %, or at least about 0.02 wt. %, or at least about 0.03 wt. %,or at least about 0.04 wt. %, or at least about 0.05 wt. %, or less thanor equal to about 10 wt. %, or less than or equal to about 9 wt. %, orless than or equal to about 8 wt. %, or less than or equal to about 7wt. %, or less than or equal to about 6 wt. %, or less than or equal toabout 5 wt. %. The compatibilizer should be selected such that most ofthe compatibilizer is reacted onto the PVB polymer, leaving little or nounreacted compatibilizer in the polymer interlayer.

In the extruder (or other mixing) device, the thermoplastic rawmaterial, recycled material and plasticizers, and any other additivesdescribed above, are further mixed and melted, resulting in a melt thatis generally uniform in temperature and composition. Once the meltreaches the end of the extruder device, the melt is propelled into theextruder die. The extruder die is the component of the thermoplasticextrusion process which gives the final polymer interlayer sheet productits profile. Generally, the die is designed such that the melt evenlyflows from a cylindrical profile out of the die and into the product'send profile shape. A plurality of shapes can be imparted to the endpolymer interlayer sheet by the die so long as a continuous profile ispresent. In some embodiments, the compatibilizer can be added intorecycled material (e.g., trilayer acoustic interlayer or other recycledmaterial, such as that comprising multiple different resins and/orplasticizers) and melt mixed together. The melt can be extruded intopellets to produce compatibilized material containing compatibilizer,which can be used later in producing polymer interlayer. Thecompatibilized material can be used to produce a monolithic interlayer,or a multiple layer interlayer in which at least one of the layerscontains compatibilized material.

Notably, for the purposes of this application, the polymer interlayer atthe state after the extrusion die forms the melt into a continuousprofile will be referred to as a “polymer melt sheet.” At this stage inthe process, the extrusion die has imparted a particular profile shapeto the thermoplastic resin, thus creating the polymer melt sheet. Thepolymer melt sheet is highly viscous throughout and in a generallymolten state. In the polymer melt sheet, the melt has not yet beencooled to a temperature at which the sheet generally completely “sets.”Thus, after the polymer melt sheet leaves the extrusion die, generallythe next step in presently employed thermoplastic extrusion processes isto cool the polymer melt sheet with a cooling device. Cooling devicesutilized in the previously employed processes include, but are notlimited to, spray jets, fans, cooling baths, and cooling rollers. Thecooling step functions to set the polymer melt sheet into a polymerinterlayer sheet of a generally uniform non-molten cooled temperature.In contrast to the polymer melt sheet, this polymer interlayer sheet isnot in a molten state and is not highly viscous. Rather, it is the setfinal-form cooled polymer interlayer sheet product. For the purposes ofthis application, this set and cooled polymer interlayer will bereferred to as the “polymer interlayer sheet.”

In some embodiments of the extrusion process, a co-extrusion process maybe utilized. Co-extrusion is a process by which multiple layers ofpolymer material are extruded simultaneously. Generally, this type ofextrusion utilizes two or more extruders to melt and deliver a steadyvolume throughput of different thermoplastic melts of differentviscosities or other properties through a co-extrusion die into thedesired final form. The thickness of the multiple polymer layers leavingthe extrusion die in the co-extrusion process can generally becontrolled by adjustment of the relative speeds of the melt through theextrusion die and by the sizes of the individual extruders processingeach molten thermoplastic resin material.

Generally, the thickness, or gauge, of the polymer interlayer sheet willbe in a range from about 15 mils to 100 mils (about 0.38 mm to about2.54 mm), about 15 mils to 60 mils (about 0.38 mm to about 1.52 mm),about 20 mils to about 50 mils (about 0.51 to 1.27 mm), and about 15mils to about 35 mils (about 0.38 to about 0.89 mm). In variousembodiments, each of the layers, such as the skin and core layers, ofthe multilayer interlayer may have a thickness of about 1 mil to 99 mils(about 0.025 to 2.51 mm), about 1 mil to 59 mils (about 0.025 to 1.50mm), 1 mil to about 29 mils (about 0.025 to 0.74 mm), or about 2 mils toabout 28 mils (about 0.05 to 0.71 mm).

As noted above, the interlayers of the present disclosure may be used asa single-layer sheet or a multilayered sheet. In various embodiments,the interlayers of the present disclosure (either as a single-layersheet or as a multilayered sheet) can be incorporated into a multiplelayer panel.

As used herein, a multiple layer panel can comprise a single substrate,such as glass, acrylic, or polycarbonate with a polymer interlayer sheetdisposed thereon, and most commonly, with a polymer film furtherdisposed over the polymer interlayer. The combination of polymerinterlayer sheet and polymer film is commonly referred to in the art asa bilayer. A typical multiple layer panel with a bilayer construct is:(glass) II (polymer interlayer sheet) II (polymer film), where thepolymer interlayer sheet can comprise multiple interlayers, as notedabove. The polymer film supplies a smooth, thin, rigid substrate thataffords better optical character than that usually obtained with apolymer interlayer sheet alone and functions as a performance enhancinglayer. Polymer films differ from polymer interlayer sheets, as usedherein, because polymer films do not themselves provide the necessarypenetration resistance and glass retention properties, but ratherprovide performance improvements, such as infrared absorptioncharacteristics. Poly(ethylene terephthalate) (“PET”) is the mostcommonly used polymer film. Generally, as used herein, a polymer film isthinner than a polymer sheet, such as from about 0.001 to 0.2 mm thick.

Further, the multiple layer panel can be what is commonly known in theart as a solar panel, with the panel further comprising a photovoltaiccell, as that term is understood by one of ordinary skill in the art,encapsulated by the polymer interlayer(s). In such instances, theinterlayer is often laminated over the photovoltaic cell, with aconstruct such as: (glass) II (polymer interlayer) II (photovoltaiccell) II (polymer interlayer) II (glass or polymer film).

The interlayers of the present disclosure will most commonly be utilizedin multiple layer panels comprising two substrates, preferably a pair ofglass sheets (or other rigid materials, such as polycarbonate oracrylic, known in the art), with the interlayers disposed between thetwo substrates. An example of such a construct would be:(glass)//(polymer interlayer sheet)//(glass), where the polymerinterlayer sheet can comprise a single layer interlayer or multilayeredinterlayers, as noted above. These examples of multiple layer panels arein no way meant to be limiting, as one of ordinary skill in the artwould readily recognize that numerous constructs other than thosedescribed above could be made with the interlayers of the presentdisclosure.

The typical glass lamination process comprises the following steps: (1)assembly of the two substrates (e.g., glass) and interlayer; (2) heatingthe assembly via an IR radiant or convective means for a short period;(3) passing the assembly into a pressure nip roll for the firstdeairing; (4) heating the assembly a second time to about 50° C. toabout 120° C. to give the assembly enough temporary adhesion to seal theedge of the interlayer; (5) passing the assembly into a second pressurenip roll to further seal the edge of the interlayer and allow furtherhandling; and (6) autoclaving the assembly at temperatures between 135°C. and 150° C. and at pressures between 150 psig and 200 psig for about30 to 90 minutes.

Other means for use in de-airing of the interlayer-glass interfaces(steps 2-5) known in the art and that are commercially practiced includevacuum bag and vacuum ring processes in which a vacuum is utilized toremove the air.

Clarity is one measure of optical quality of a laminate. Clarity isdetermined by measuring the haze value or percent haze (% haze) and/orthe percent transmittance (% T). Haze is a percentage of transmittedlight that is scattered so that its direction deviates more than aspecified angle from the direction of the incident beam. Haze may bemeasured using a haze meter or a spectrophotometer, such as HunterLabUltraScan XE instrument, or other haze meter known to one of skill inthe art, and in accordance with ASTM D1003-Procedure B using IlluminantC, at an observer angle of 2 degrees. Percent transmittance (% T) orTransparency, is the percentage of the total incident light transmittedthrough the specimen, and is determined according to ASTM D1003 as well.The improved polymer compositions and interlayers comprising thecompositions of the present disclosure have a percent haze of less thanabout 5%, or less than about 4.5%, or less than about 4%, or less thanabout 3.5%, or less than about 3%, or less than about 2.5%, or less thanabout 2%, or less than about 1.5%, or less than about 1%, or less thanabout 0.5%. The improved polymer compositions and interlayers comprisingthe compositions of the present disclosure have a % T of greater than70%, or greater than 75%, or greater than 80%, if the interlayer is aclear interlayer. Interlayers having dyes or pigments may have a % Tthat is lower, as desired.

The glass transition temperature also is used to describe the polymerinterlayers of the present disclosure. The glass transition temperature(T_(g)) was determined by dynamical mechanical thermal analysis (DMTA).The DMTA measures the storage (elastic) modulus (G′) in Pascals, loss(viscous) modulus (G″) in Pascals, loss (damping) factor (LF)[tan(delta)] of the specimen as a function of temperature at a givenfrequency and temperature sweep rate. A frequency of 1 Hz andtemperature sweep rate of 3° C./min were used herein. The T_(g) is thendetermined by the position of the loss factor peak on the temperaturescale in ° C.

The invention also includes Embodiments 1 to 19, as set forth below.

Embodiment 1 is a polymer composition comprising: a first poly(vinylbutyral) resin having a first residual hydroxyl content; a secondpoly(vinyl butyral) resin having a second residual hydroxyl content; aplasticizer; and at least one compatibilizer; wherein the differencebetween the first and second residual hydroxyl contents is at least 2wt. %, and wherein the polymer composition has a percent haze of lessthan 5% (as measured in accordance with ASTM D1003-Procedure B usingIlluminant C).

Embodiment 2 is a polymer composition including the features ofembodiment 1, where the polymer composition comprises from about 0.01wt. % to about 10 wt. % compatibilizer.

Embodiment 3 is a polymer composition including the features of any ofembodiments 1 to 2, wherein the compatibilizer is an anhydridecompatibilizer.

Embodiment 4 is a polymer composition comprising: a first poly(vinylbutyral) resin having a first residual hydroxyl content; a secondpoly(vinyl butyral) resin having a second residual hydroxyl content; aplasticizer; and from 0.01 to 10 wt. % of at least one anhydridecompatibilizer; wherein the difference between the first and secondresidual hydroxyl contents is at least 2 wt. %, and wherein the polymercomposition has a percent haze of less than 5% (as measured inaccordance with ASTM D1003-Procedure B using Illuminant C).

Embodiment 5 is a polymer composition including the features of any ofembodiments 1 to 4, wherein the compatibilizer comprises at least oneanhydride having Structure (3), Structure (4), Structure (5) orStructure (6):

wherein R may be hydrogen or a saturated or unsaturated carbon chain offrom 1 to 16 carbon atoms.

Embodiment 6 is a polymer composition including the features of any ofembodiments 1 to 5, wherein the compatibilizer comprises at least twoanhydrides.

Embodiment 7 is a polymer composition including the features of any ofembodiments 1 to 6, wherein the compatibilizer is at least one ofhexahydro-4-methylphthalic anhydride, hexahydrophthalic anhydride,phthalic anhydride, 3,4,5,6-tetrahydrophthalic anhydride, or2-octen-1-ylsuccinic anhydride.

Embodiment 8 is a polymer composition including the features of any ofembodiments 1 to 7, wherein the compatibilizer comprises a mixture ofhexahydrophthalic anhydride and hexahydro-4-methylphthalic anhydride.

Embodiment 9 is a polymer composition including the features of any ofembodiments 1 to 8, where the polymer composition comprises from about0.05 wt. % to about 5 wt. % compatibilizer.

Embodiment 10 is polymer interlayer including the features of any ofembodiments 1 to 9.

Embodiment 11 is a multiple layer polymer interlayer comprising: a firstlayer comprising a first poly(vinyl butyral) resin having a firstresidual hydroxyl content and a plasticizer; a second layer comprising asecond poly(vinyl butyral) resin having a second residual hydroxylcontent and a third poly(vinyl butyral) resin having a third residualhydroxyl content, a plasticizer, and at least one compatibilizer;wherein the difference between the second and third residual hydroxylcontents is at least 2 wt. %, and wherein the polymer interlayer has apercent haze of less than 5% (as measured in accordance with ASTMD1003-Procedure B using Illuminant C).

Embodiment 12 is a polymer interlayer including the features ofembodiment 1, where the polymer interlayer comprises from about 0.01 wt.% to about 10 wt. % compatibilizer.

Embodiment 13 is a polymer interlayer including the features of any ofembodiments 11 to 12, wherein the compatibilizer is an anhydridecompatibilizer.

Embodiment 14 is a polymer interlayer including the features of any ofembodiments 11 to 13, wherein the compatibilizer comprises at least oneanhydride having Structure (3), Structure (4), Structure (5) orStructure (6):

wherein R may be hydrogen or a saturated or unsaturated carbon chain offrom 1 to 16 carbon atoms.

Embodiment 15 is a polymer interlayer including the features of any ofembodiments 11 to 14, wherein the compatibilizer comprises at least twoanhydrides.

Embodiment 16 is a polymer composition including the features of any ofembodiments 11 to 15, wherein the compatibilizer is at least one ofhexahydro-4-methylphthalic anhydride, hexahydrophthalic anhydride,phthalic anhydride, 3,4,5,6-tetrahydrophthalic anhydride, or2-octen-1-ylsuccinic anhydride.

Embodiment 17 is a polymer interlayer including the features of any ofembodiments 11 to 16, wherein the compatibilizer comprises a mixture ofhexahydrophthalic anhydride and hexahydro-4-methylphthalic anhydride.

Embodiment 18 is a polymer composition including the features of any ofembodiments 11 to 17, where the polymer composition comprises from about0.05 wt. % to about 5 wt. % compatibilizer.

Embodiment 19 is a multiple layer glass panel including the polymerinterlayer of any of embodiments 11 to 18.

EXAMPLES

The improvements (or reduction) in the level of haze in a polymerinterlayer when combining resins having different residual vinyl alcoholcontent in the presence of a compatibilizer, such as an anhydridecompatibilizer, can be readily appreciated by a comparison ofcompositions using multiple resins and a compatibilizer to sampleshaving multiple resins without the addition of a compatibilizer, asdiscussed below.

A ‘virgin’ composition (“virgin PVB”) was formed by mixing 100 partspoly(vinyl butyral) resin having 18 to 19 weight percent residualhydroxyl groups and 2 weight percent of a residual vinyl acetate, 38parts of plasticizer, and other common additives used in interlayers.This virgin composition was further mixed with various amounts ofdifferent compatibilized or un-compatibilized recycle material and meltprocessed into polymer interlayers.

The compatibilized recycle PVB materials were produced by mixing andmelt-processing different mixtures of recycle material with variousamounts of anhydride compatibilizers into pellets or flakes (using adevice such as a twin-screw extruder, or a single screw extruder, or aBanbury-type mixer). The recycle PVB (“recycle PVB”) material used wastrilayer acoustic PVB material having skin layers comprising plasticizedpoly(vinyl butyral) resin layers having about 18 to 19 weight percentresidual hydroxyl groups and a vinyl acetate residue of 2% and having atotal thickness of 28 mil, and a core layer comprising a plasticizedpoly(vinyl butyral) resin layer having about 10 to 11 weight percentresidual hydroxyl groups and a vinyl acetate residue of 2% and havingthickness of 4.5 mil.

The compatibilized recycle materials can also be produced by mixingvirgin composition, comprising 100 parts poly(vinyl butyral) resinhaving 18 to 19 weight percent residual hydroxyl groups and 2 weightpercent of a residual vinyl acetate, 38 parts of plasticizer, othercommon additives used in interlayers, and recycle PVB material, andvarious amounts of anhydride compatibilizers, and then melt extrudingthe mixtures into pellets or flakes (using a device such as a twin-screwextruder, or a single screw extruder, or a Banbury-type mixer). Theresults are as shown in Table 1 to Table 4 below for each of theExamples.

Example 1

Control samples containing various levels (3, 10, 30, 40 and 100%) ofrecycle PVB with the remainder virgin composition (virgin PVB) (exceptfor Sample A1 which was 100% recycle PVB) were produced. Nocompatibilizer was added. The materials were melt mixed in a Brabender™mixer and melt compressed into sheet samples using a steam-heatedpresser to form a sheet having a thickness of about 0.76 mm (30 mil).The sheets were then laminated between two pieces of clear glass (90 milthickness) and tested. Percent haze was measured on the laminatesamples, and the results are shown in Table 1 below.

TABLE 1 Sample Wt. % of Recycle PVB % Haze (30 mil) A1 100 19.30 C1 403.45 A7 30 1.60 A6 10 1.15 A5 3 0.97

Table 1 shows that even at low levels (3 to 10 wt. %) of addition of therecycle PVB, the resulting percent haze of the laminate may beunacceptable. For example, Sample A5 has a percent haze level of about1%, but only 3% recycle PVB was added. For Samples A6 and A7 (10 and 30%recycle PVB respectively), haze level increased to more than 1%. Atlevels of 40 and 100%, the haze significantly increased. The amount ofhaze generally acceptable to many industrial applications, such asautomotive and architecture applications, is below about 1%. As shown inTable 1, as the amount of recycle PVB in the composition increases, thepercent haze also increases, as shown by Samples A1, C1 and A5 to A7.

Example 2

In Example 2, hexahydro-4-methylphthalic anhydride (HHMPA) in varyingamounts (from 2.13 wt. % to 6.76 wt. %) was added to the mixturescomprising 40 to 100 wt. % recycle PVB and 60% to 0% virgin PVB. Thematerials were melt mixed in a Brabender mixer and melt compressed intosheet samples using a steam-heated presser to form a sheet having athickness of about 0.76 mm (30 mil). The sheets were then laminatedbetween two pieces of clear glass and tested. Control samples having nocompatibilizer (A1 and C1) from Table 1 above are shown for comparison.Samples A1 to A4 were samples of 100% recycle PVB; Samples B1 and B2comprised 50% recycle PVB and 50% virgin PVB; and Samples C1 and C2comprised 40% recycle PVB and 60% virgin PVB. Percent haze was measuredon all laminate samples, and the data is shown in Table 2 below.

TABLE 2 Wt. % of Compatibilizer - Sample Wt. % of Recycle PVB HHMPA %Haze (30 mil) A1 100 0 19.30 A2 100 2.13 16.25 A3 100 4.17 14.05 A4 1006.10 8.95 B1 50 4.17 5.60 B2 50 6.76 2.90 C1 40 0 3.45 C2 40 5.70 1.40

Table 2 demonstrates that the percent haze is at the highest level forthe control samples having no compatibilizer, and as compatibilizer isadded to the blend of recycle and virgin PVB, the haze level decreases.Comparing Sample A1 to Samples A2, A3 and A4, as increasing amounts ofanhydride compatibilizer (from 2.1 to 6.1 wt. % respectively) were addedto the blends, the haze, which was 19.30% in Sample A1 (with nocompatibilizer), dropped as the amount of compatibilizer increased. Withthe addition of 6.10 wt. % of compatibilizer, percent haze wassignificantly (less than half) reduced from 19.30% to 8.95% (Sample A4).Comparing Samples C1 and C2, adding 5.7 wt. % anhydride compatibilizerto the samples with 40% recycle PVB reduced the haze by more than 50%,from 3.45% (Sample C1) to 1.40% (Sample C2). Samples B1 and B2additionally confirm that increasing the amount of anhydridecompatibilizer reduces the haze levels.

Example 3

The compatibilized material made in Sample A3 (100% recycle PVB with4.17% HHMPA compatibilizer) or Sample A4 (100% recycle PVB with 6.10%HHMPA compatibilizer) was added at varying amounts from 10 to 30 wt. %into virgin PVB and melt mixed and melt compressed into sheet samplesand then laminated as described above. Percent haze was measured on thelaminate samples, and the results are shown in Table 3 below.

TABLE 3 Wt. % of Wt. % of Compatibilized Compatibilized Recycle PVB ofRecycle PVB of Sample Sample A3 Sample A4 % Haze (30 mil) D1 10 0.45 D220 0.65 D3 30 0.95 E1 10 0.40 E2 20 0.50 E3 30 0.65

Table 3 shows that when compatibilized recycle PVB is added into virginPVB at levels of up to 30 wt. % and melt mixed and melt compressed intosheet samples, the resulting percent haze is still lower than the hazeof Sample A5, which is the sample containing only 3% recycle PVB withouta compatibilizer. Therefore, much higher levels of recycle PVB, such asup to at least 30% recycle PVB, can be added into the virgin compositionand used to produce a quality interlayer having acceptably low hazelevels. This is in contrast to samples without a compatibilizer, whereonly about 3% of the recycle PVB could be added without causing haze orclarity problems.

Comparing Sample D3 to Sample A7, both samples had 30 wt. % recycle PVBadded, but the recycle PVB added to Sample A7 was not compatibilized. Asshown in Table 3, the percent haze of Sample D3 was much less than thatof Sample A7 (or, stated differently, the percent haze of Sample A7 isover 50% higher at 1.60 versus 0.95 for Sample D3). Comparing Sample D1to Sample A6 shows a similar result, where 10 wt. % of recycle PVB wasadded. In the compatibilized blend (Sample D1), the resultant haze was0.45, compared to 1.15 (Sample A6) where no compatibilizer was added.Comparing Sample E3 to Sample A7, both samples had 30 wt. % recycle PVB,but the recycle PVB in Sample A7 was not compatibilized, and thereforethe resulting percent haze level was much higher than that in Sample D3(1.60% versus 0.65%, or over 100% higher), which containedcompatibilized recycle PVB. Comparing Sample E1 to Sample A6 shows asimilar result, where each sample contained 10 wt. % of recycle PVB. Inthe compatibilized blend of Sample E1, the resultant haze was 0.40%,compared to a haze level of 1.15% where no compatibilizer was added.This can also be demonstrated by comparing Sample A5 to Sample E3, whereeven at an addition level of 30 wt. % of the compatibilized recycle PVB,the resulting percent haze of Sample E5 is still lower than the haze ofSample A5, which only had 3 wt. % recycle PVB (0.65% versus 0.97%).

Further, a comparison of the results in Table 3 shows that for sampleshaving a higher level of anhydride compatibilizer (6.10 wt. % versus4.17 wt. %), the resultant percent haze for samples having the samelevel of recycle PVB is lower, particularly at higher levels of recyclePVB material (compare Sample D3 with Sample E3).

Example 4

Samples were also prepared using a different anhydride compatibilizer,phthalic anhydride (PA), at different levels of compatibilizer. Amountsof compatibilizer and resulting haze are shown below in Table 4. Allmixtures in Table 4 contain 40% recycle PVB and 60% virgin PVB as wellas the amount of phthalic anhydride shown in the table. The samples weremelt mixed at different temperatures as indicated in Table 4 for 7minutes and then melt compressed into sheet samples, and then laminatedand tested for % Haze (as described above). Results are shown in Table4.

TABLE 4 Wt % of Mixing Compatibilizer Temperatures Sample PA (° C.) %Haze F1 0 170 3.15 G1 1 170 2.55 H1 2 170 2.60 I1 4 170 2.10 F2 0 1904.70 G2 1 190 2.40 H2 2 190 2.30 I2 4 190 2.25

Table 4 shows that a different compatibilizer, phthalic anhydride, canalso be used in blends containing recycle PVB to effectively reduce thepercent haze level and improve the clarity of the resulting interlayer.Table 4 also shows that although percent haze is effectively reducedwhen phthalic anhydride compatibilizer is used compared to samples withno compatibilizer (Samples F1 and F2), the mixing temperature (170° C.vs. 190° C.) had very little effect on the resulting percent haze.

In conclusion, the Examples show that the compositions and interlayerscomprising blends of multiple resins having differing residual vinylalcohol levels and a compatibilizer, such as an anhydridecompatibilizer, as described herein, have advantages over interlayerscomprising blends of similar resins without the anhydridecompatibilizer, as previously utilized in the art. In general, use of acompatibilizer, such as an anhydride compatibilizer, results insignificantly increased compatibility of the resins, which results in apolymer composition (and an interlayer comprising the composition)having good clarity (i.e., lower percent haze), good color, reducedtransmission loss, and therefore improved optical quality interlayers.Use of an anhydride compatibilizer results in significantly increasedrecyclability of different PVB materials or resins having differentproperties, such as different residual hydroxyl content. Otheradvantages will be readily apparent to those skilled in the art.

While the invention has been disclosed in conjunction with a descriptionof certain embodiments, including those that are currently believed tobe the preferred embodiments, the detailed description is intended to beillustrative and should not be understood to limit the scope of thepresent disclosure. As would be understood by one of ordinary skill inthe art, embodiments other than those described in detail herein areencompassed by the present invention. Modifications and variations ofthe described embodiments may be made without departing from the spiritand scope of the invention.

It will further be understood that any of the ranges, values, orcharacteristics given for any single component of the present disclosurecan be used interchangeably with any ranges, values or characteristicsgiven for any of the other components of the disclosure, wherecompatible, to form an embodiment having defined values for each of thecomponents, as given herein throughout. For example, an interlayer canbe formed comprising poly(vinyl butyral) having a residual hydroxylcontent in any of the ranges given in addition to comprising aplasticizers in any of the ranges given to form many permutations thatare within the scope of the present disclosure, but that would becumbersome to list. Further, ranges provided for a genus or a category,such as anhydrides, can also be applied to species within the genus ormembers of the category, such as hexahydro-4-methylphthalic anhydride orphthalic anhydride, unless otherwise noted.

1. A polymer composition comprising: a first poly(vinyl butyral) resinhaving a first residual hydroxyl content; a second poly(vinyl butyral)resin having a second residual hydroxyl content; a plasticizer; and atleast one compatibilizer; wherein the difference between the first andsecond residual hydroxyl contents is at least 2 wt. %, and wherein thepolymer composition has a percent haze of less than 5% (as measured inaccordance with ASTM D1003-Procedure B using Illuminant C).
 2. Thepolymer composition of claim 1, comprising from about 0.01 wt. % toabout 10 wt. % compatibilizer.
 3. The polymer composition of claim 1,wherein the compatibilizer is an anhydride compatibilizer.
 4. Thepolymer composition of claim 1, wherein the compatibilizer comprises atleast one anhydride having Structure (3), Structure (4), Structure (5)or Structure (6):

wherein R may be hydrogen or a saturated or unsaturated carbon chain offrom 1 to 16 carbon atoms.
 5. The polymer composition of claim 1,comprising from about 0.05 wt. % to about 5 wt. % compatibilizer.
 6. Thepolymer composition of claim 1, wherein the compatibilizer comprises atleast two anhydrides.
 7. The polymer composition of claim 1, wherein thecompatibilizer is at least one of hexahydro-4-methylphthalic anhydride,hexahydrophthalic anhydride, phthalic anhydride,3,4,5,6-tetrahydrophthalic anhydride, or 2-octen-1-ylsuccinic anhydride.8. The polymer composition of claim 1, wherein the compatibilizercomprises a mixture of hexahydrophthalic anhydride andhexahydro-4-methylphthalic anhydride.
 9. A polymer interlayer comprisingthe polymer composition of claim
 1. 10. A multiple layer polymerinterlayer comprising: a first layer comprising a first poly(vinylbutyral) resin having a first residual hydroxyl content and aplasticizer; a second layer comprising a second poly(vinyl butyral)resin having a second residual hydroxyl content and a third poly(vinylbutyral) resin having a third residual hydroxyl content, a plasticizer,and at least one compatibilizer; wherein the difference between thesecond and third residual hydroxyl contents is at least 2 wt. %, andwherein the polymer interlayer has a percent haze of less than 5% (asmeasured in accordance with ASTM D1003-Procedure B using Illuminant C).11. The polymer interlayer of claim 10, comprising from about 0.01 wt. %to about 10 wt. % compatibilizer.
 12. The polymer interlayer of claim10, wherein the compatibilizer is an anhydride compatibilizer.
 13. Thepolymer interlayer of claim 10, wherein the compatibilizer comprises atleast one anhydride having Structure (3), Structure (4), Structure (5)or Structure (6):

wherein R may be hydrogen or a saturated or unsaturated carbon chain offrom 1 to 16 carbon atoms.
 14. The polymer interlayer of claim 10,wherein the compatibilizer is at least one of hexahydro-4-methylphthalicanhydride, hexahydrophthalic anhydride, phthalic anhydride,3,4,5,6-tetrahydrophthalic anhydride, or 2-octen-1-ylsuccinic anhydride.15. The polymer interlayer of claim 10, wherein the compatibilizercomprises a mixture of hexahydrophthalic anhydride andhexahydro-4-methylphthalic anhydride.
 16. A polymer compositioncomprising: a first poly(vinyl butyral) resin having a first residualhydroxyl content; a second poly(vinyl butyral) resin having a secondresidual hydroxyl content; a plasticizer; and from 0.01 to 10 wt. % ofat least one anhydride compatibilizer; wherein the difference betweenthe first and second residual hydroxyl contents is at least 2 wt. %, andwherein the polymer composition has a percent haze of less than 5% (asmeasured in accordance with ASTM D1003-Procedure B using Illuminant C).17. The polymer composition of claim 16, wherein the compatibilizercomprises at least one anhydride having Structure (3), Structure (4),Structure (5) or Structure (6):

wherein R may be hydrogen or a saturated or unsaturated carbon chain offrom 1 to 16 carbon atoms.
 18. The polymer composition of claim 16,wherein the compatibilizer is at least one of hexahydro-4-methylphthalicanhydride, hexahydrophthalic anhydride, phthalic anhydride,3,4,5,6-tetrahydrophthalic anhydride, or 2-octen-1-ylsuccinic anhydride.19. The polymer composition of claim 16, wherein the compatibilizercomprises a mixture of hexahydrophthalic anhydride andhexahydro-4-methylphthalic anhydride.
 20. A polymer interlayercomprising the polymer composition of claim 16.